Draftsman&#39;s rule



July 19, 1938. 1 v CANTRELL 2,124,051

DRAFTSMAN S RULE Filed Feb. 24, 1937 IN VEN TOR Lorraine l/ Cantrell BY q ATTORNEY Patented July 19, 1938 UNITED STATES PATENT OFFIE 2 Claims.

My invention relates to draftsmens rules, and more particularly to an architects and engineers rule which may be read in interchangeable units and fractions of units.

Among the objects of my invention are: To provide a rule having interchangeable unit markings and interchangeable vernier movements; to provide a self-reading rule for architects and engineers wherein the vernier movements may be read upon an enlarged scale; to provide a rule in units and fractions of units which may be easily read with great accuracy; and to provide a rule having removable and interchangeable combinations of units and fractions thereof which is adaptable for use where units of different character are involved.

Other objects of my invention will be apparent or will be specifically pointed out in the description forming a part of this specification, but I do not limit myself to the embodiment of the invention herein described, as various forms may be adopted within the scope of the claims.

In the drawing illustrating a preferred embodiment of my invention, Figure 1 is a top view of one form of my invention.

Figure 2 is a sectional view taken by the line 2-2 in Figure 1.

Figure 3 is a sectional View taken as indicated by the line 33 in Figure 1.

Figure 4 is a sectional view taken as indicated by the line 44 in Figure 1; and

Figure 5 is an enlarged view of a removable vernier movement.

My invention may be more fully understood by direct reference tothe preferred embodiment shown herein.

A rule frame I is provided with a unit scale 2 graduated in one particular type of units, as for example, in feet, as the illustrations herein show a foot scale. The foot scale 2 fits over the bottom of the frame I and is held thereto by an inturned front edge 3 and an inturned back edge I. The scale, therefore, may he slid onto the frame from one end, and is pushed on until the zero end abuts a scale stop 5. Once in that position it is locked to the frame by a locking screw 6. The scale is preferably provided at each unit mark with marking recesses I. Telescoping into the frame I is a vernier extension II) having thereon an end stop II in the same line as that projected from the main scale 2, the entire edge of this stop thus providing a convenient locating point for initiating the measurement.

The vernier extension I is operated by a thumb screw I2, preferably located at the right end of the scale, and drives through worm gear I4 a longitudinal threaded rod I5. The end of the rod I is firmly attached to a spline block I6 mounted in a bearing II. The spline block is pro-- vided with a diametrical slot I9 into which is inserted a vernier screw block 20, the head of which fits the spline block recess in such a manner that the vernier block will rotate with the screw block I6 and will also be prevented from coming out of the block. Vernier screw block 20 has an axial threaded bore therein into which is fitted a vernier screw 2| terminating in a square flanged head 22, dropping into a square slot in a vernier positioning block 24 which is firmly attached to the vernier extension III.

Thus it will be seen that when the thumb screw I2 is rotated the vernier extension will be moved outwardly or inwardly in accordance with the pitch of the screw 2|. Inasmuch as the pitch of the screw ZI must necessarily be different for difierent scales, I have provided on the upper side of the scale frame I a hinged window 26, which may be opened, and when the vernier screw block and screw are in their maximum engagement the entire assembly of vernier block and screw may be removed from the scale by sliding the assembly upward out of the respective engagements with the terminal block, and a new block and screw inserted. The cover when closed prevents the vernier screw and block from moving out of engagement with their terminal blocks. At the same time, the vernier block 20 can be seen through the transparent cover 26, and I may prefer tomark upon the vernier screw block 20 the ratio of vernier extension with respect to the units used.

The indication of the amount of extension of the vernier portion of the scale is given by an enlarged vernier scale 21 positioned under vernier scale window 28, and the indication of the position of the vernier extension III with respect to this scale is given by an indicator block 29, traveling on screw thread I5 and carrying an index pointer 30 projecting over the scale 21. Inasmuch, however, as several different vernier scales are to be used, as determined by the vernier block, I prefer to mark the enlarged vernier scale 2! on the periphery of a rotatable cylinder 3| rotated by a scale wheel 32 projecting through the frame. I have found that at least three, and possibly more, scales can be inscribed on the periphery of this cylinder.

In operation, the proper unit scale desired is slipped onto the frame and fixed. The scale Wheel 32 is then rotated until the proper fractions appear beneath the vernier scale window. For example, I have shown feet on the scale 2, and therefore a 12-inch scale on the vernier cylinder. Under these circumstances, then, the proper vernier block and screw 20 and 2| are inserted to move the vernier so that the index pointer 30 will move the full scale range, while the vernier extension I 0 is moving the distance representing one foot as determined by scale 2. If, however, the measurements are to be taken in some other units and the vernier read in tenths, then the thumb screw 32 may be rotated to bring an enlarged tenths scale under the vernier window 28, the corresponding vernier block and screw inserted, and, if desired, a new main unit scale 2 substituted for the one shown. .Under these circumstances it can be seen that this scale may be equipped With accessory vernier screws and main scales together with a proper enlarged scale that will give measurements of practically all the units and fractions of units utilized in draftsmanship. Furthermore, the scale can be adapted to any reduction ratios desired.

The use of the rule has been found to increase the speed of scaling for architects and engineers, it produces greater accuracy, and makes the work of scaling much easier for the operator.

I claim:

1. A draftsmans rule comprising a frame, a removable and interchangeable scale mounted thereon and abutting a stop on said frame, a vernier extension telescoping into one end of said frame and having an index point thereon lining up with said scale, an enlarged scale mounted on said frame, a rotatable screw having a pointer actuated by rotation of said screw and moving along said enlarged scale, and means for extending said vernier extension by rotation of said screw by an amount reduced in distance but in proportion to the divisions of said enlarged scale.

2. A draftsmans rule comprising a frame, a removable and interchangeable scale mounted thereon and abutting a stop on said frame, a vernier extension telescoping into one end of said frame andhaving an index point thereon lining up with said scale, an enlarged scale mounted on said frame and calibrated in fractions of the units of said removable scale, a rotatable screw having a pointer actuated by rotation of said screw and moving along said-enlarged scale, a reduction screw and thread linking said rotatable screw and said extension whereby said extension will be moved by rotation of said screw by an amount reduced in distance but proportional to the calibrations of said enlarged scale and in fractions of the units of said removable scale.

LORRAINE V. CANTRELL. 

